Surfactants are materials used to address problems in areas relating to altering conditions at interfaces. For example, surfactants are used as detergents, emulsifiers, wetting agents, anti-static agents and the like, where changes in liquid-liquid or liquid-air interfaces are needed. Also, surfactants may be used when conditions at solid-liquid interfaces require alteration, such as reduction of friction at solid surfaces. A specific use of surfactants involves their ability to lower critical surface tensions of liquids, promoting better "wetting" of surfaces.
One effective solution to the problem of reducing altering conditions at interfaces is through the use of fluorosurfactants. These compounds fall into two major classes: ionic and nonionic. Ionic fluorosurfactants are characterized by a long chain perfluorocarbon lyophobic tail and a polar (cationic or anionic) head. These types of compounds usually form micelles when they are present in systems above their critical micelle concentration (CMC).
As the name implies the molecules of the nonionic fluorosurfactants do not contain an ionic head. The lyophilic end of the molecule results from a water soluble polymer or oligomer block of an alkylene oxide, for example, ethylene oxide.
Fluorosurfactants may be used to stabilize aqueous emulsions of perfluorinated fluorinated hydrocarbons. These materials act as oxygen and carbon dioxide transport agents useful as blood substitutes in mammals.
U.S. Pat. No. 3,472,894 discloses perfluoroalkyl ether bis(hydroxyalkyl) amides of the formula R.sub.f O(C.sub.3 F.sub.6 O).sub.n CF(CF.sub.3)CON(C.sub.p H.sub.2p OH).sub.2 useful as surface active agents.
U.S. Pat. No. 3,547,995 discloses perfluoroalkyl ether amidoamine oxides of the formula R.sub.f O(C.sub.3 F.sub.6 O).sub.n CF(CF(CF.sub.3)CON(R')Q in which Q is selected from certain radicals containing an amine oxide group useful as surface active agents.
U.S. Pat. No. 3,600,415 discloses fluoronated amides useful as oil-repelling agents having the structural formula ##STR2## where R.sub.f is a fluorine-containing isoalkoxyalkyl group and R is a divalent alkylene bridging group.
U.S. Pat. No. 3,621,059 discloses amides derived from hexafluoropropylene oxide polymer acids and polyalkylene oxide having the formula ##STR3## useful as surfactants and emulsifying agents.
U.S. Pat. No. 3,828,085 discloses amidoamine oxides of the formula ##STR4## where R.sub.f is a perfluoroalkyl group or a polyfluoroisoalkoxyalkyl group useful as surface active agents.
U.S. Pat. No. 4,079,084 discloses fluorocarbon surfactants containing a nonionic hydrophilic chain (preferably an oxyethylene chain) and at least two terminal perfluorocarbon groups of at least three carbon atoms, preferably branched perfluorocarbon groups derived from an oligomer of tetrafluoroethylene.
U.S. Pat. No. 4,171,282 discloses perfluoroalkylthio-substituted half esters and amides of succinic acid having the formula ##STR5## where Y is R.sub.f --R'--S--(CH.sub.2).sub.y useful as surfactants. J. Afzal, et al., J. of Fluorine Chem., 34 (1987) 385-393 discloses monodisperse perfluoroalkyl N-polyethoxylated amides C.sub.n F.sub.2n+1 CONH(CH.sub.2 CH.sub.2 O).sub.m H as potential nonionic fluorinated surfactants.